Voice control is unresponsive after updating to sequoia

My computer updated to Sequoia last night, and now I cannot get voice control to work consistently. When I first turn the computer on, it works fine, but after a few minutes it stops responding to my voice. It responds to "wake up" and "go to sleep" but nothing else. I cannot dictate text, cannot open or close programs, or use my voice to navigate the operating system or websites. It doesn't respond when I give it the "show numbers" command, or ask it to click on anything. When I restart the computer, it works initially, but then goes back to ignoring everything except for waking up and going to sleep.